Been running 4.3 for a few days, and personal hotspot work great on the Rogers network in Canada. A little bit of latency, but at least 3 Mbps down and almost 1 Mbps up.. Excellent feature. Takes away the requirement for a 3G iPad...
The biggest reason to get a 3G iPad 2 if you already have an iPhone 4 is for the GPS IMO. I use my iPad 3G GPS so I would miss it in the iPad 2. Also, buying a 3G iPad allows month by month payment for data so if you only need cellular data on your iPad occasionally it may be cheaper to go that route than paying for personal hotspot every month..